UNIX for Dummies Questions & Answers

file1:
X    Y
=========
x1  y2
x3  y4
x2  y4
x5  y3
=========
file2:
Y   Z
=========
y1  z1
y2  z2
y3  z3
y4  z4
y5  z5


Finally these result should look like:
X    Y   Z
=========
x1  y2  z2
x3  y4  z4
x2  y4  z4
x5  y3  z3
=========

awk 'NR==FNR {a[$1]=$2; next} $2 in a {print $0, a[$2]}' f2 f1

#!/bin/sh

INPUT_PATH="/home/"
INPUT_FILE1="${INPUT_PATH}sample2.file1.txt"
INPUT_FILE2="${INPUT_PATH}sample2.file2.txt"
OUTPUT_FILE="${INPUT_PATH}sample2.file.out"
DUMMY_INPUT="${INPUT_FILE1}.dummy"

# Add the second column of file2 to file1 as the 3rd column
# Note: The 3rd column values corresponds to the values of the 2nd column

HEADER=`cat ${INPUT_FILE1} | sed q`
GRID=`cat ${INPUT_FILE1} | sed '$!d'`
DEL_HEADER=`cat ${INPUT_FILE1} | sed '1,2d' | sed '$d' > ${DUMMY_INPUT}`

echo "${HEADER}   Z" >> ${OUTPUT_FILE}
echo "${GRID}=" >> ${OUTPUT_FILE}

while read LINE
do
        REF_FILE1=`echo ${LINE} | awk '{ print $2 }'`
        REF_FILE2=`grep ${REF_FILE1} ${INPUT_FILE2} | awk '{ print $2 }'`
        echo "${LINE}  ${REF_FILE2}" >> ${OUTPUT_FILE}
done < ${DUMMY_INPUT}

echo "${GRID}=" >> ${OUTPUT_FILE}

rm ${DUMMY_INPUT}

exit

join -1 2 -2 1 -o 1.1 0 2.2 <( sort -k2,2 $FILE1 ) <( sort -k1,1 $FILE2 )

x1 y2 z2
x5 y3 z3
x2 y4 z4
x3 y4 z4